#int(input())
#map(int, input().split())
#list(map(int, input().split()))

N = int(input())
S = input()

mod = 998244353

t = 1

m = N

fac = [1] * (m+1)
facinv = [1] * (m+1)

for i in range(1, m+1):
    fac[i] = (fac[i-1] * i) % mod
    facinv[i] = (facinv[i-1] * pow(i, mod-2, mod)) % mod

def nCk(n, k):
    return (fac[n] * facinv[k] * facinv[n-k]) % mod

from collections import Counter

c = Counter()

a = S.count("A") + S.count("B")

print(nCk(N, a))